Not Applicable.
This invention relates generally to orthodontic devices and, in particular, to an improved device for treating an underbite, specifically a Class III malocclusion.
Class III malocclusions occur in about 4% of the Caucasian population but are quite prevalent in the Asian populations. Generally, Class III malocclusion or underbite in an adult or non-growing patient is corrected by an orthognathic surgical operation which requires surgically breaking the jaw and moving the maxilla anteriorly or moving the mandible posteriorly, or both. It would be advantageous, therefore, to have an orthodontic appliance that can be employed to correct underbite in an older or non-growing patient in order to avoid oral surgery.
In this application, a new a contracting sheath connector for attachment between the maxilla and mandible is provided. The contracting sheath can be connected between a maxillary molar or maxillary appliance and a mandibular appliance.
The contracting sheath includes a hollow posterior tube, a hollow anterior tube, and a rod extending through the two tubes. The anterior and posterior tubes are threadably connected so that the overall length of the advancing sheath can be selectively altered. An attachment is provided at a forward end of the posterior tube to pivotally mount the posterior tube to a tooth band. Another attachment is provided at the back end of the rod to pivotally connect the rod to a second tooth band. A spring is provided which extends between a forward end of the anterior tube and a forward end of the posterior tube. The spring urges the anterior tube rearwardly relative to the posterior tube to compensate for jaw pressure and to help prevent the jaw pressure from threading the anterior tube rearwardly.
In one embodiment, the posterior tube is externally threaded and the anterior tube is internally threaded. In this embodiment, the spring is journaled about the posterior tube. The posterior tube is provided with a stop forwardly of the end of the anterior tube, and the spring is positioned between the posterior tube stop and the forward end of the anterior tube. In a second embodiment, the posterior tube is internally threaded, and the anterior tube is externally threaded. In this embodiment, the spring is received within the hollow posterior tube and is journaled about the rod.
The expansion complex includes an outer housing and an advancing member which is telescopically received in the outer housing. The two portions of the expansion complex are received in opposed halves of a plate which fits against the mandibular or maxillary arch.
The outer housing includes side walls, a top, a bottom, a back, and an open front. A channel is formed in the housing top and extends rearwardly from the front of the housing. A threaded rod extends forwardly from the housing back wall beneath the channel to be accessible through the channel. At least one post (and preferably two posts) extend from the housing back wall parallel to the threaded rod.
The advancing member includes side walls, a bottom, a top, and a front wall. The advancing member is sized and shaped to beslidably received in the outer housing. A channel is formed in the advancing member top and extends rearwardly from the front wall. The advancing member channel is aligned with the outer housing channel.
To move the advancing member, an activation nut is threadably received on the threaded rod. The nut is accessible through the channels and movable along the threaded rod by rotation of the nut. An activation wing has a first plate slidably received on the threaded rod in front of the activation nut and a second plate slidably received on the post. The first and second plates are operatively connected to each other, and movement of the activation nut moves the first plate, and hence the second plate, relative to the housing and the advancing member. A spring is journaled about the post between the activation wing second plate and the advancing member front wall. When the spring is compressed, it effectively applies a pressure to the arch to force expansion of the arch.
Guides are provided to facilitate movement of the advancing member relative to the housing. The grooves of the outer housing and the advancing member are both defined by sloped walls, and the sloped walls of the advancing member channel are adjacent the sloped walls of the housing channel. Additionally, a groove is provided in the bottom surface of the advancing member and a corresponding rib is formed on the inner surface of the housing bottom. The rib and groove interaction, as well the interaction of the sloped walls, act as the guides for the movement of the advancing member.